Panicking is the simplest error handling mechanism in Rust.
You can use the panic! macro to panic the current thread. It prints an error message, unwinds and cleans up the stack, and then exits the program.
Let’s try calling the panic! macro in a simple program:
fn main() { panic!("At The Disco"); }
This program would exit with status code 101 and print the following message:
thread 'main' panicked at 'At The Disco', panic.rs:2:5
The preceding panic message reveals the place in the source code where the panic occurred, panic.rs:2:5. The message indicates that it’s the fifth character on the second line of the panic.rs file.
In general terms, you should use panic! when a program reaches an unrecoverable state meaning anything where there is absolutely no way to recover from the error.
Rust panics on some operations such as a division by zero or an attempt to access an index that isn't present in an array, a vector, or a hash map, as shown in the following code:
let v = vec![0, 1, 2, 3];
println!("{}", v[6]); // this will cause a panic!